Molecular imaging collectively refers to a number of techniques that enable researchers to observe genes, proteins, and other molecules performing a variety of functions in the body, and they have rapidly progressed, thanks to advances in cell biology, biochemical materials, and computer analysis. Unlike X-ray, ultrasound, and other conventional techniques which give doctors only such anatomical clues as the size of a tumor, molecular imaging could help tackle the underlying causes of disease, because it shows the motion of tumors at the molecular level. It has been reported that such molecular imaging techniques will substitute for breast X-ray examination, tissue biopsy and other biopsies in the future.
Many studies on magnetic nanoparticles as contrast agents for use in molecular imaging technology have been conducted. Korean Patent Registration 541282 discloses a technique capable of specifically recognizing liver cells using superparamagnetic iron oxide nanoparticles as liver contrast agents. U.S. Pat. No. 6,638,494 discloses paramagnetic nanoparticles containing a metal such as iron oxide, U.S. Pat. No. 5,746,999 discloses coating silica on the surface of paramagnetic nanoparticles containing a metal such as iron oxide, complexing the nanoparticles with dextran, and applying the resulting nanoparticles in in vivo magnetic resonance imaging, and Korean Patent Publication 2007-0058358 discloses a magnetic resonance imaging agent containing magnetic manganese oxide nanoparticles.
Various attempts to apply such magnetic particles in the medical and pharmaceutical field have been continued, and the results of such research have been applied in industrial practice. However, there is a problem in that it is not easy to apply such magnetic particles to in vitro studies such as cell studies, because an external strong magnetic field must be used in order to use magnetic properties.
Recently, a patent application relating to magnetic nanoparticles, which have optical properties and magnetic properties simultaneously and are covered with a silica shell, was filed (Korean Patent Publication 2007-0029030). However, in said patent application, fluorescent materials exhibiting optical properties are limited to organic fluorescent materials, and magnetic nanoparticles, which can be finally obtained, are also limited to water-soluble magnetic nanoparticles. In addition, there is a technical problem in that the silica shell must be surface-modified in a separate process in order to contain the organic fluorescent materials.
Meanwhile, as contrast agents for use in such molecular imaging technology, complex agents containing perfluorocarbon have recently been widely used. This is because it is known that perfluorocarbon (hereinafter referred to as PFC) does not cause carcinogenesis, mutation and teratogenesis, has low viscosity, excellent emulsifying properties, high gas solubility, lubricating properties, magnetic susceptibility close to that of water, shows non-immune responses and is physiologically inactive and biocompatible. Particularly, perfluorocarbon has been studied for the purpose of delivering bioactive materials to local sites and for therapeutic purposes (Gregory, M. et al., Current Topics in Developmental Biology, 70:57, 2005; Krafft, M. P., Advanced Drug Delivery Reviews, 47:209, 2001).
Accordingly, there is an urgent need to develop particles which have fluorescent properties observable and measurable in vitro and, at the same time, are also applicable in vivo. However, the results of studies on such particles are still insufficient.
Accordingly, the present inventors have made extensive efforts to solve the problems occurring in the prior art and, as a result, have found that a multifunctional perfluorocarbon nanoemulsion, which can simultaneously perform magnetic resonance imaging (MRI) and optical imaging (OI), can be prepared by dispersing quantum dot nanoparticles modified with a fluorine end group in perfluorocarbon and then adding an aqueous emulsifier solution containing lipid to the dispersion, thereby completing the present invention.